A road repair team built 215 full-length roads on the first day and 12 full-length roads on the second day. At this time, there are still 1800 meters to reach the midpoint of the road. How long is the road?

A road repair team built 215 full-length roads on the first day and 12 full-length roads on the second day. At this time, there are still 1800 meters to reach the midpoint of the road. How long is the road?

1800 △ 12 − 215-215 × 12, = 1800 △ 12-15, = 1800 △ 310, = 1800 × 103, = 6000 m; a: this road is 6000 m long

Xiao Li can get to the school in time by walking at 5km / h. once, he got on the bus at 20km / h after walking 2 / 3 of the whole journey, so he got to the school 15 minutes earlier than the original time. How far is his home from the school?
How many 2.8 meters per second did a and B catch up with each other at the same time?
3 a self driving team was trained. All the members of the trainer moved forward alone at the speed of 3km/h. Suddenly, the number 1 marched forward at 45km/h speed. After marching 10km, the car turned back at the speed of 45km/h until it joined the other players. How many minutes did the.1 team start from the departure team and the rendezvous with the players?
There is a project that needs 20 minutes, 30 minutes and 40 minutes for a, B and C to complete alone. Now three people cooperate and start work at the same time. A leaves for a few minutes in the middle of the project for some reason. As a result, the project is completed 12 minutes after the start of the project?
5. There is a pool filled with water from two water pipes. The first pipe is filled in 2 hours and 30 minutes, and the second pipe is filled in 5 hours
(1) If the cooling water pipes of Party A and Party B are filled with water for 20 minutes at the same time, how long does it take to fill them up?
(2) Suppose that the drainage pipe C is placed under the pool, and a full pool can be discharged after only opening C for 3 hours. If three pipes are opened at the same time, how many hours can an empty pool be filled with water?
6. Party A and Party B go from place a to place B 51 kilometers away at the same time. Party A rides a bike and Party B walks. The speed of Party A is three times faster than that of Party B by 1 km / h. after arriving at place B, Party A has a rest for an hour and a half, and then returns to place A. on the way, they meet Party B. Party A and Party B are just 6 hours away from their departure time. What are their respective speeds?

1. Suppose that the distance from his home to school is x km, X △ 5 - (2x / 3 △ 5 + 1x / 3 △ 20) = 1 / 4, and the solution is x = 52. Suppose that it takes x seconds 2.4x-0.8x = 200X = 1253 for B to catch up with a in the second time. Suppose that it takes x hours 45x + 3x = 10 × 2x = 5 / 125 / 12 hours = 25 minutes for No

The following is a mathematical problem. It's best to write the idea of solving the problem!
A good horse runs 240 Li a day, a bad horse 150 Li a day, and a bad horse runs 12 days first. How many days can a good horse catch up with a bad horse?

It is known that a good horse runs 240 miles a day and a bad horse 150 miles a day
A good horse catching up with a bad horse is their equal distance
Let's catch up in X days
Therefore, 150 * 12 + 150 * x = 240 * x
So x = 20
So I caught up in 20 days